Metal oxides are used for a variety of reasons, including as pigments, in many industries including the food and beverage industry, dairy industry, pharmaceutical industry, and cosmetic industry. In other industries, such as the semiconductor industry, metal oxides are a by-product of manufacturing. These metal oxides are known to cause soiling.
The dairy industry is increasingly using metal oxides, and titanium dioxide in particular, in dairy products, and low fat dairy products. Adding titanium dioxide to low fat dairy products such as milk, yogurt, cheese, sour cream, cottage cheese, cream cheese and butter whitens the product to provide the appearance of a higher fat content. Titanium dioxide has been added to dairy products since the 1970's.
Generally, titanium dioxide has been added to dairy products prior to pasteurization. The pasteurization step involves heating the dairy product. As a result of heating, titanium dioxide has an increased tendency to soil the surface it contacts. In addition to building up on and around the heat exchanger, the titanium dioxide is known to deposit on other pieces of processing equipment where there may be low flow or indirect spraying of the milk product.
In recent years, the United States Department of Agriculture has focused attention on titanium dioxide soiling in dairy facilities. Efforts have been directed to addressing titanium dioxide soiling. See U.S. Pat. No. 5,763,377 to Dobrez et al.
Prior cleaning products have been used in the cleaning of dairy facilities having titanium dioxide soiling. The EVAP-O-KLEEN® cleaning product from Ecolab Inc. has been used since the early 1980's in these facilities. The EVAP-O-KLEEN® cleaning product is an aqueous composition containing a mixture of nitric acid and phosphoric acid, and an organic surfactant. The EVAP-O-KLEEN® cleaning product has been used to provide CIP (clean-in-place) cleaning in dairy facilities for removal of mineral buildup such as titanium dioxide soiling, and for leaving the equipment surfaces bright and shiny. Typically, surfaces with titanium dioxide soiling have a white, cloudy appearance. CIP cleaning generally refers to the cleaning of processing equipment in a circuit without the disassembly of large processing equipment which is often too expensive.
The pharmaceutical industry uses metal oxides such as titanium dioxide as a pigment, for example, in the coatings of pills. This titanium dioxide builds up on the processing equipment, creating a white, cloudy soil. The pharmaceutical industry has a “zero tolerance” for any soil on the equipment. This means that during cleaning any visible soil, such as titanium dioxide must be cleaned off the equipment. In the pharmaceutical industry, some equipment is cleaned using a clean-in-place system, however, many pieces of equipment are cleaned manually, which is time consuming and costly.